Below is a tutorial based on Claudio’s tutorial, but I cut out the unnecessary stuff and add a section on how to assign user to group visually (for newbies and ultra-beginner like me).

Install VirtualBox in Ubuntu

Download the .deb file here. Choose your appropriate OS and download. This is the binaries version and also a deb file so it would be very easy to install.
Note: Do not use Synaptic to install OSE package. It did not work for me. The x86 version is for intel, and amd64 is for AMD chips.

Double click on the .deb package to install. There will be several announcement makes during installation, but don’t worry, we will take care of it.

We need to add users into vboxusers in order to use VirtualBox. Follow the instructions below. We can do it graphically.

Assigning Users to Group – Graphic

System -> Administration -> Users and Groups

Select Unlock.

Enter your Password and click Authenticate.

Select Manage Groups.

Double click on vboxusers group or select it and click Properties to edit group.

Check the members you would like to add to the group, make sure you are one of them.

OK and close. You have added users into group.

You are now able to use VirtualBox. Below is a good youtube tutorial, check it out if you like.

I just installed Virtual box a few days ago to run Windows inside Ubuntu. But after messing with group permission and upgrades, there was an error similar to the one below.

Could not load the settings file ‘/home/MyUsername/.VirtualBox/OpenSUSE 10.3.xml’ (VERR_OPEN_FAILED).

FATAL ERROR: Unknown element ‘PXEDebug’

Whatever it was, I kept getting it after multiple removals and reinstallations. Ubuntu forum did not have a solution, or at least not the one that worked for me. So, I decided to come up with a solution myself and it was incredibly simple. The goal is to remove the .xml file and then reinstall VirtualBox.

Solution

Entering Synaptic.

Search for “virtualbox” and uninstall all VirtualBox packages.

Then open your home folder,

On the menu bar, select View -> Show hidden files and folder.

Delete the folder called “.VirtualBox“. This will erase the annoying .xml file.

Reinstall VirtualBox like usual. For instruction on how to install, visit Ubuntu community.